The federal government Friday said that it had tentatively decided to permit a field test in the Florida Keys of genetically engineered mosquitoes that might be effective in limiting the spread of the Zika virus.

The Food and Drug Administration said it had made a preliminary determination that the field trial was unlikely to cause harm to people, animals or the environment.

However, a final approval for the trial will not be made until the FDA receives and assesses comments from the public, which is likely to take months.

The mosquitoes, developed by a British company, Oxitec, contain a gene that kills the insect. Male mosquitoes containing the gene are released to mate with wild females. Offspring from such matings die before they reach adulthood and in that way suppress the population of wild mosquitoes that can spread diseases like Zika and dengue fever.

The mosquitoes have already shown some effectiveness in suppressing mosquito populations in small tests in Brazil and some other countries.

But efforts by Oxitec and the Florida Keys Mosquito Control District to test them in the community of Key Haven, outside Key West, have run into opposition from some residents, who worry about unexpected consequences.